The term “optical device” refers to a broad range of devices that require control and/or manipulation of light, including those utilized in photovoltaics, light emission, photo-detection, and photo-catalysis. In many of these applications, the optical device is protected or enclosed in packaging glass that acts not only to protect the active region of the optical device, but to efficiently transmit light to or from the active region. Optical packaging glass has a relatively low refractive index, and is therefore a good choice for protecting/encasing the active regions of optical devices as light is allowed to travel relatively freely through the packaging glass. Typically, packaging glass would have a flat or planar surface. However, somewhat counterintuitively, a flat surface does not provide the best performance. In particular, a flat surface has several drawbacks including relatively high reflection rates (i.e., light incident to the surface is reflected back away from the active region of the optical device) and relatively low self-cleaning capabilities (e.g., particles adhere relatively easily to the flat surface structure, resulting in obscuration of light incident to the surface of the packaging glass.
For example, in solar cell applications, it is important for the packaging glass selected to transmit a high percentage of the incident sunlight to the active region of the solar cell (i.e, low reflectivity). In addition, because solar cells are used outdoors over extended periods of time, it is important for the surface of the packaging glass to provide good self-cleaning capabilities in order to reduce the amount of dust/particles that adhere to the surface of the packaging glass. This is particularly important for applications in which the solar cell will be utilized in dusty/polluted areas.